1. Field of the Invention
The present invention relates to a production method of a suspension board with circuit and, more particularly, to a production method of a suspension board with circuit having a ground terminal.
2. Description of the Prior Art
In recent years, improvements in transmission speed and transmission accuracy are increasingly demanded for storage units, such as computers and their peripheral devices. In the circumstances, there are increasing tendencies to use high-frequency signals for electric signals. But, noises in electric signals transmitted increase with frequency.
In general, a suspension board with circuit mounted on a hard disc comprises an insulating layer formed on a metal foil serving as a metal board, and a conductor layer serving as a conductive pattern formed on the insulating layer (Cf. JP Laid-open (Unexamined) Patent Publication No. Hei 10-265572, for example). In this suspension board with circuit, difference in the electrical potentials between the metal board and the conductive pattern can cause noise generation.
In order to reduce the noises, the suspension board with circuit is structured so that a ground terminal is formed in the conductive pattern to put the conductive pattern in conductive relationship with the metal board, so as to allow the conductive pattern to connect with the ground by connecting the ground terminal of the conductive pattern with a ground terminal of an electronic component such as a magnetic head.
Also, in order to prevent corrosion, a gold plating layer is formed on the ground terminal of the conductive pattern by electrolytic gold plating.
The gold plating layer is formed on the ground terminal in the following manner. First, the suspension board with circuit 1 before configured is covered with a plating resist 17 so that only a ground terminal 13 forming portion of the conductive pattern 7 can be exposed from the plating resist 17, as shown in FIG. 5(a). Then, a gold plating layer 12 is formed on the ground terminal 13 forming portion of the conductive pattern 7 by electrolytic gold plating, while feeding electric power from the metal board 2, as shown in FIG. 5(b). Thereafter, the plating resist 17 is removed, as shown in FIG. 5(c). In FIG. 5, the same reference numerals and marks are labeled to corresponding parts to those shown in FIG. 1.
In the method illustrated above, since the electric power is fed from the metal board 2, the whole area of the suspension board with circuit 1 except the ground terminal 13 forming portion of the conductive pattern 7 must be covered with the plating resist 17, in order to prevent the gold plating layer 12 from being formed on the metal board 2. On the other hand, the formation of the plating resist 17 and the subsequent removal process of the same require cumbersome and complicated processes, such as adhesion, exposure-to-light, development, and stripping of the plating resist 17, thus causing production cost increase.